This invention relates generally to a device for supporting and aligning photographic masters used in producing images on both sides of a photographic medium, and particularly to a chase for producing aperture patterns on kinescope shadow mask material.
During the production of shadow masks for color television picture tubes, a large strip of thin metal is coated on both sides with a photoresist material. The coated material is passed through an exposure device, typically called a chase, which supports two photographic plates. The photographic plates include the aperture patterns which are to be exposed onto both sides of the shadow mask material. Both sides of the material are flooded with light while the mask material rests between the two masters. The unexposed photoresist material is washed away leaving the desired apertures unprotected. The material is passed through an acid tank and the apertures are etched through the material. Because etching occurs from both sides of the metal, the aperture patterns on the two sides of the material must be properly aligned. Accordingly, the photographic plates must be precisely aligned in the chase prior to the light exposure. The maintenance of precise alignment of the photographic plates is difficult because the frames in which the plates are mounted must be opened and closed during the insertion and removal of the metal. This repeated opening and closing of the frames causes the bearings, joints and other elements to wear and develop play which makes the maintenance of alignment very difficult, or impossible. Another disadvantage of existing chases arises because the plates are placed into the chase from the top, thereby requiring the operator to stand on a ladder while inserting and removing the plates.
The instant invention overcomes these problems by the provision of a chase in which the photographic plates are easily aligned while firmly held in the chase, and in which the plates are readily accessible to the operator for changing and aligning.